Already posted this in the 2.5l specific section but turned up few results so I figured I'd repost it here...

Car is a 2012 Golf 2.5l. Going back to last year, the car developed a misfire across all cylinders and eventually died on the highway. Engine would crank but not start. New coil packs were installed and problem was solved.

A few months ago, car developed a very similar misfire. (Slight misfires noticed at idle, heavy stumbling under medium/heavy acceleration, between 2500-4500rpm.) I installed another new set of coil packs and the engine will crank all day long but won't start. Crank position sensor was replaced, spark plugs were replaced, even tried two other sets of coil packs and nothing will work. The strangest part is that when I reinstall the old burned up coil packs, the car will start up just fine, it will just continue running with the random misfire. At this point I know it's just a matter of time before the coil packs actually fail and I'm left on the side of the highway again. I know the new coils shouldn't be the problem because I've tried them in two other 2.5l's and both cars started up just fine.

I've talked to a number of VW service centers, fellow enthusiasts, and even put a call in to VW America and NOBODY has an answer. If anyone has any idea why the car will run will the old coil packs but won't start with brand new OEM coils it would be appreciated. Thanks.

the r8 coil packs that people use on gti's work great on 2.5's as well. If your OLD coil packs work, then the new ones are definitely faulty.

One of the new sets I tried were OEM red tops from ECS. The other set were OEM black tops directly from VW. Both work fine when installed on my buddy's 2.5l, but the minute I put them in my car it will crank but won't start.

Quick update on the issue...I test fitted 5 new coil packs this morning (the cheap Denso ones from Advance Auto that were previously in the car) and the car fired right up first try...Got home and put in the R8 red tops and they still won't fire...is it possible that the ECU adapted to the cheap coil packs and now will only run with that specific type?

I've never heard of a car adapting so much to a specific component like that, but now I'm wondering if a complete ECU reset will fix the problem. I tried touching the +/- terminals together to reset it that way but it didn't change anything. Maybe a full adaptation reset with VAGCOM?

Quick update on the issue...I test fitted 5 new coil packs this morning (the cheap Denso ones from Advance Auto that were previously in the car) and the car fired right up first try...Got home and put in the R8 red tops and they still won't fire...is it possible that the ECU adapted to the cheap coil packs and now will only run with that specific type?

I've never heard of a car adapting so much to a specific component like that, but now I'm wondering if a complete ECU reset will fix the problem. I tried touching the +/- terminals together to reset it that way but it didn't change anything. Maybe a full adaptation reset with VAGCOM?

Didn't realize the red tops from ECS were different from actual R8 coils but that's good to know for future reference. As far as the parts being faulty, I just find it strange that 3 separate sets of coil packs, (one set from ECS, two sets of OEM coil packs direct from VW) would all be faulty...especially when they work perfectly fine when installed on a different car...it was only when they were installed on my car that they wouldn't fire.

I think you already solved the issue. If they are working on other cars... but not yours, and your old ones work... that has to be the issue you need to resolve. It's usually a straight swap however as you're experiencing results outside the normal I would start there. Might not be the coil packs

Didn't realize the red tops from ECS were different from actual R8 coils but that's good to know for future reference. As far as the parts being faulty, I just find it strange that 3 separate sets of coil packs, (one set from ECS, two sets of OEM coil packs direct from VW) would all be faulty...especially when they work perfectly fine when installed on a different car...it was only when they were installed on my car that they wouldn't fire.